The present invention relates to the general field of fabricating gas turbine casings, and more particularly retention casings for a gas turbine fan of an aeroengine.
In a gas turbine aeroengine, the fan casing performs several functions. It defines the air inlet passage into the engine, it supports an abradable material facing the tips of the fan blades, it optionally supports a structure for absorbing soundwaves in order to provide acoustic treatment at the inlet of the engine, and it incorporates or supports a retention shield. Such a shield constitutes a trap for retaining debris, such as articles that have been ingested or fragments of damaged blades that are projected outwards by centrifuging, so as to prevent them passing through the casing and reaching other portions of the aircraft.
Proposals have already been made to make a fan casing out of composite material. By way of example, reference may be made to Document EP 1 961 923, which describes fabricating a casing out of composite material and of thickness that varies, the method including forming a fiber preform by superposing layers of a fiber texture and then densifying the fiber reinforcement with a matrix. More precisely, that document makes provision to use a take-up mandrel for three-dimensionally weaving the fiber texture, which texture is then wound as superposed layers on an impregnation mandrel that presents an outside surface of profile that corresponds to the profile of the central portion of the casing that is to be fabricated, together with two lateral rims corresponding to fastener flanges of the casing. The fiber preform is held on the impregnation mandrel and it is impregnated with resin before polymerizing the resin.
In order to impregnate the fiber preform by a resin transfer molding (RTM) type injection method, it is known to position the elements of a mold cover on the impregnation mandrel so as to form an injection mold. By way of example, reference may be made to Document WO 2013/060978, which discloses putting angular sectors into place in order to close the resin injection mold on the impregnation mandrel. Nevertheless, closing the mold as described in that document raises several problems. In particular, its angular sectors do not provide uniform compacting of the fiber preform, since the pressure that is applied can vary from one sector to another and it need not be applied solely towards the fiber preform. Furthermore, sealing between two adjacent angular sectors can be unsatisfactory, thereby reducing the reliability of the mold during injection of the resin.
Consequently, there exists a need for an injection mold that does not present sealing problems while injecting resin, and that ensures that the compacting of the fiber preform is uniform.